What do I do when I have shit ton work to do at three in the morning? I impulsively write smut, yes, yes I do. Enjoy.
Disclaimer: I own nothing but my own very pervy mind.
Sherlock takes it as an issue of personal pride to excel at everything he takes an interest in, and it would be idiotically unnecessary to reiterate something so blatantly obvious as him being a quick study. So of course he's good at the mechanics of sex. He plays John, at the risk of using a tedious metaphor, like his violin, twisting fingers in perfect time with staccato breaths and applying his tongue at just the right patch of skin, with just the right pressure, to make him gasp and squeeze his eyes shut helplessly before tearing them open again. But that's not why he makes John Watson come harder than he ever has before, in over twenty years of sexually active adult life. No, Sherlock makes him come like he's turning inside out, like he's forgotten his own name, because of the way he looks at him.
The detective never takes his eyes of him unless it's absolutely necessary, and even then, he returns to staring as soon as possible. Because that's what it is, staring. It's unnerving. He observes every quiver in John's lip, every dilation of his pupils, hell, every bead of sweat squeezing from trembling pores. He watches the evolution of John's orgasm play out over his face, from the first seductive glance to the moment he grunts out the syllables of Sherlock's name in release. For the entirety of the erotic act, Doctor John Watson holds the world's only consulting detective's undivided attention.
By this time Sherlock's got him reacting like Pavlov's dogs. All he has to do is look at John with that steady, appraising interest, like he's simultaneously considering forty-one different aspects to some fascinating puzzle, and all John's blood flows directly to his cock. It's the weight of that gaze that gets him off every time, as much as Sherlock's skillful ministrations. Even when John's behind him, buried balls deep in his ass and panting like dog, the detective can't help but put cricks in his neck twisting his head around to watch.
Sherlock's watching drives him to distraction every time, and is the reason he's more sexually satisfied than he would have dreamed possible. But what John really loves, what curls up in his chest and makes his mouth "o" and his brows crinkle up in awe, are those heavy seconds Sherlock closes his eyes. When John brings him to the edge and sends him tumbling over, and for once the doctor sees deeper into his detective than he could ever see into him.